Aircraft tail structures have grown in surface area and frontal area. Attitude control mechanisms convert directive signals of humans and instruments into powered actuators which partially rotate airfoil surfaces. Powered systems for pitch and yaw control of aircraft harbor potential failure modes.
e.g. Safety-of-flight was brought to National television screens on Jul. 19, 1989, when a United Airline aircraft attempted an emergency landing at Sioux City Iowa, after its powered pitch control system had been damaged during flight. The pilot maintained heroic pitch control with other power and control options, however a fuguoidal nose-down oscillation during final approach induced a crash with loss of life.
Aircraft in flight can tolerate severe damage and survive if the pilot can retain aircraft pitch control, however, failure of powered control surfaces exaggerates pitch-control problems:
Servo-tabs at the trailing edge of elevator surfaces were are linked through handles, cables, pulleys, and lever arms to augment rotational capability of tail surfaces of older A/C.
Those trailing hinge-surface tabs rotated oppositely from intended rotational movement of aft elevator plates to which they are were attached. Air driven forces from the tabs helped actuate the hinged-plate airfoils against air-fluid forces of flight. Paradoxically, the direct force from the servo-tabs was opposite from the pilot-intended tail reaction.
Pilot and autopilot commands to move airfoil control surfaces for modern, very large aircraft pass from the cockpit to tail surface actuators through electric communication, (fly by wire) wherein original commands are reconverted into mechanical action with electro-mechanical apparatus, frequently including hydraulic systems.
Ref: McGraw Hill Encyclopedia of Technology.
"Flying tail" elevator systems combine horizontal stabilizers of a front portion and hinged aft plates of a rear portion into a "Stabilator" U.S. Pat No. 4,781,341. Airframe-mounted power sources of large aircraft connect and rotate these combined cantilever structures. Some large aircraft designs connect control surface power sources independently to cantilevered horizontal stabilizers and to cantilevered elevators shaped as hinged aft plates.
Growth of aircraft size has drawn special dependence on powered subsystems, and in parallel has introduced a need for alternative backup systems.
Fence spoilers, arising through the top surface of WWII very large fighter aircraft (P-61) replaced ailerons. Flat spoiler surfaces, perpendicular to flying airloads, were manually lifted above the forward wing airfoil to kill center-of-wing lift in proportion to their extended height and in accordance with Bernoulli lift phenomena. EQU (e.g.) Pressure+1/2Density (Velocity)(Velocity)=Constant.
Hinge spoilers are powered to rotate upwardly from aft wing sections of heavy aircraft to resist air pressure of forward motion, to kill some aft lift during landing and to augment aileron forces during slow flight. (U.S. Pat. No. 3,618,878) Arnquist.
Hinge spoilers are rectangular flat surfaces, rotationally attached to a top surface plane of an airfoil, and usually located along the aft edge of an inboard section of a wing or elevator plate.